In an authentication context aimed at authenticating a client against a service using cryptographic key material, access is granted or denied based on cryptographic evidence that the authenticating client has control over a specific key part, only known to the client, in the case of an asymmetric cryptographic approach, or shared between the client and the service provider, in the case of a symmetric cryptographic approach. Various standards and technologies are employed to accomplish the authentication of a client to a service, server, or peer such as X.509 certificates and related public key infrastructure (PKI) used in Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL), Secure Shell (SSH) and its related infrastructure, and other such technologies.
With the proliferation of sensitive and private information that is stored on and carried by computers, devices, networks and so forth, security and privacy have become increasingly important. Also, significant efforts have been devoted to minimizing attack surfaces in networks to enhance security.